The decision to remove Drive Extender from the next version of Windows Home …

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Microsoft's Windows Home Server is a funny little product. The company's ambition when developing the product was to have us all run little home servers: small, low-power, appliance-like machines with some network connectivity and gobs of storage. We'd use these home servers as a place to back up our PCs, share files and printers across our home networks, stream media to our Xboxes, and gain remote access to our files when away from home.

In practice, most of these things can be done perfectly well with a normal desktop version of Windows. Windows Home Server does have some advantages—it had a management front-end that let the server be easily controlled remotely, and it is based on Windows Server 2003 to slim down its own hardware demands—but for the most part, it isn't doing anything too unusual. As a result, Windows Home Server has remained a niche product. Much loved by its users, but never really making it as a mass-market success.

It does, however, have one special feature, a feature without any real equivalent in any other version of Windows, whether for desktop or for server. That feature is called Drive Extender. Conceptually, Drive Extender is quite simple: it allows multiple hard disks (regardless of interface or size) to be aggregated to provide a single large pool of storage. Folders on the pooled storage could also be selectively replicated, meaning that Drive Extender would ensure that copies of the files were found on multiple physical disks.

For a home fileserver, this is obviously a very handy capability. It allows simple ad hoc expansion of storage—no RAID rebuilding, no need to match disk capacities, no need to stick to any drive interface—and does so without the inconvenience of multiple drives, each of which has to have its free space managed manually.

For Windows Home Server's small, but vocal, following, Drive Extender is arguably the most important feature. It's what makes Windows Home Server something better than simply plugging some USB disks into a PC. Without Drive Extender, Windows Home Server as a product makes a lot less sense.

Indeed, Drive Extender was fundamental to the home server concept. A home server as originally envisaged by the Windows Home Server team should have, in essence, infinite storage, and storage that should be transparently extensible. This is why RAID, though common in corporate environments, isn't an viable solution for most home users. With RAID, you can't simply add another disk whenever you need more space. RAID requires management and planning.

Enter "Vail"

Windows Home Server version 2, codenamed "Vail," is currently in development. It is intended to give Windows Home Server richer backup capabilities, and to make it more extensible and simpler to set up and use.

Vail betas have, until now, also included a new and improved Drive Extender—one designed to make this key feature more robust and reliable. "Until now," because Microsoft has just announced that Vail will no longer include Drive Extender. Arguably the most significant feature of Windows Home Server, now gone.

The response from Vail testers and Windows Home Server users alike has been astonishment and outrage. A bug raised against Vail demanding the feature's restoration was filed almost immediately after the announcement, and has rapidly accrued hundreds of votes and many angry comments. This is not a popular decision at all, with many of the complainants saying that Drive Extender was the only reason they used Windows Home Server in the first place.

Drive Extender was also set to be a feature of the forthcoming Small Business Server 2011 Essentials (codename "Aurora") and Windows Storage Server 2008 R2 Essentials (codename "Breckenridge") products, giving it reach beyond the consumer market. Microsoft, for its part, says that after soliciting feedback from both consumers and small businesses, it no longer saw a need for the feature. Large hard drives are now readily available, and Microsoft is saying that these represent an adequate alternative to the Drive Extender technology.

With the removal of Drive Extender, it's hard to see what the point of Windows Home Server really is. A Drobo is probably a better solution for most file storage needs, and tasks like printer sharing and remote access are either built in to Windows anyway or available with free Windows software like Windows Live Mesh. Without the expandable storage, Windows Home Server's role as a file server, surely its raison d'être, is severely compromised.

The only winners from this decision are hardware companies. Aurora and Breckenridge customers will just buy RAID systems instead, and customers after Vail-like functionality will buy Drobo units.

The real reason for its cancellation

The current Windows Home Server's Drive Extender implementation is actually pretty peculiar. Disks pooled together in Windows Home Server are just regular NTFS-formatted disks. You can take them out of the server, plug them into another machine, and see all the files. There's nothing fancy going on with the disks themselves. Instead, Drive Extender provided a fileshare that gave a unified view of all these pooled disks. Behind the scenes, the software would periodically copy files between the physical disks in order to ensure that any folders that were meant to be duplicated indeed were.

This worked, more or less, but it wasn't entirely robust. Data loss bugs cropped up when, for example, using Office documents on the pooled share afflicted Windows Home Server, and these persisted long after the product's initial release. To this day, Drive Extender can change the timestamps of files that it duplicates. These flaws are likely the reason that the technology was never used in any other products.

With Vail, Drive Extender was completely rewritten in a manner that should make it both more flexible and more reliable. Instead of using regular NTFS disks, Vail inserts a layer underneath the filesystem. This layer was responsible for distributing blocks of data between disks, replicating them to ensure fault tolerance, and de-duplicating them to make the system more efficient (something especially valuable for a backup server). The problems with the old system—corruption of in-use files, delays before files are duplicated, incompatibility with EFS encryption, errors in timestamps—were banished for good with this new layer.

These changes caused some backlash among the Windows Home Server community, as they meant forfeiting the ability to just take a drive out of a Windows Home Server system and stick it in another machine to access its files. Many users felt this to be a significant step backwards.

They are wrong. The new layer resolved many fundamental flaws with the previous mechanism, and could have served as a foundation for building even richer capabilities in the future, in a way that the old (current) Drive Extender just can't. Giving up the ability to use the disks outside of the server is, in the long run, a price worth paying.

Unfortunately, the new block layer in Vail doesn't quite work right. Just like Drive Extender in Windows Home Server, there have been bugs. Different bugs, but bugs all the same. Microsoft hasn't gone into explicit detail about what these problems are, but there were some issues with its ability to correct errors, and some Small Business Server testers reported application compatibility problems.

So instead of fixing the flaws, and potentially delaying the three products dependent on Drive Extender, Microsoft is killing the feature altogether.

Broader implications

Windows Home Server is being ruined because of issues that affected Small Business Server workloads, and as a result Vail will be, for most or all users, basically pointless. Windows Storage Server 2008 R2 Essentials, which is essentially Windows Home Server for small businesses, is also badly hurt by the decision; perhaps not quite as badly, due to greater use of RAID hardware in its target market, but it nonetheless loses a lot of flexibility.

The impact on Small Business Server 2011 Essentials and Windows Storage Server 2008 R2 Essentials is smaller, partly because it's not a regression (there is no pre-existing user base expecting this functionality), and partly because they still do other things that justifies their existence. Small Business Server 2011 Essentials should be the cornerstone of a small company's office network; while enriching its file server abilities is useful, the loss isn't catastrophic.

The bigger problem is that this decision means that Windows is still no closer to having the kind of flexible, powerful storage subsystem that is a feature of competing platforms like Linux and Solaris, as well as dedicated hardware devices like the various Drobo boxes. Advanced filesystems like the Sun-developed ZFS include this kind of flexible block storage, and the new Drive Extender was the first step towards giving Windows similar capabilities.

The current Drive Extender was clearly never going to be able to deliver this kind of flexibility, which is why it never saw any usage beyond the current Windows Home Server version. But the new Drive Extender was intended for more than just Windows Home Server: its design and features were believed to be good enough for real server workloads. These are features Windows should have, and something that Microsoft needs to get working. Even without Vail, this is work that Microsoft should be doing.

If Microsoft is going to stick with its decision and remove Drive Extender across the board, the company might as well cancel Windows Home Server altogether. I think, however, this is a bad decision.

A better solution would be to take the time to make the new-style Drive Extender work. Ship Aurora according to the current schedule (it's due some time next year), but delay Vail and Breckenridge until the feature works. Once it's robust, retrofit the feature back into Aurora as a downloadable extra, and make it a built-in component of Windows 8's corresponding server version.

Windows Home Server needs Drive Extender. The Windows platform as a whole needs Drive Extender. Hobbling Vail, and removing Drive Extendor, cannot be the right thing to do.

161 Reader Comments

Windows Home Server version 2, codenamed "Fail," is currently in development. It is intended to make Windows Home Server more extensible, simpler to set up and use, and give it richer backup capabilities.

Fail betas have, until now, also included a new and improved Drive Extender—one designed to make this key feature more robust and reliable. "Until now," because Microsoft has just announced that Fail will no longer include Drive Extender. Arguably the most significant feature of Windows Home Server, now gone.

T,FTFY.

On topic: I never used it since I never even got a good windows(cross-os, so 7, vista and xp) network running.

Windows Home Server version 2, codenamed "Fail," is currently in development. It is intended to make Windows Home Server more extensible, simpler to set up and use, and give it richer backup capabilities.

Fail betas have, until now, also included a new and improved Drive Extender—one designed to make this key feature more robust and reliable. "Until now," because Microsoft has just announced that Fail will no longer include Drive Extender. Arguably the most significant feature of Windows Home Server, now gone.

delays before files are duplicated- because people really need to backup their porn the very first second they copy it to hard drive

incompatibility with EFS encryption- again, to encrypt all the porn?

errors in timestamps- not very important except for photo (for me anyways)

Business may care about those things, but then they probably don't need to store a huge amount of files either. MS can just ship the current drive extender to the home server and disable it by default on SBS. The current version works well for home users. Without it WHS doesn't offer much than a NAS.

Oh well, the only reason I have one is because it was free by purchasing a slightly over price laptop. Bought the laptop for $800, sold it for $600 and have my WHS for $200. <3 Acer.

I was planning to rebuild my WHS box when Vail came out, as the hardware is getting a bit old - overs six years now - but this makes Vail a non- starter for me. I'm still going to do the rebuild at some point, as I don't want it to fail suddenly and then do the same rebuild as an emergency, but unless it shops with DE added back in, I'll stick to WHS v1. I can't justify spending $500-800 on a RAID controller, not for a home server.

I haven't tested it, but it seems like it does the exact same thing that Drive Extender does. That means one can build a linux-based file server without raid (and without windows licensing), and still get the "main" feature of WHS.

On another notion - thanks Ars! I've been looking around for a new storage-solution for my home data, and I considered WHS up until this article. Time to go linux, it seems.

Looks like it may be Amahi for me next. I was already leaning away from Vail as it is 64bit only and I am running my WHS on and atom board. I liked that I could use an ultra low power solution. If DE is gone and 64 bit only I'll just ride out my current WHS until something breaks, then look to linux for a solution. Microsoft never ceases to amaze me at their short sightedness.

... unless Microsoft have figured out that the Drive Extender functionality being under the FS may as well be incorporated into NTFS properly and thus bring a ZFS-like file system to all Windows boxes regardless of version.

In the age of 'tier 1' filesystems like ZFS and Btrfs, 'tier 2' fs's like ext2/3/4, HFS+ and NTFS are already obsolete and need to be upgraded to tier 1 FS's again.

Don't even get me started on the debacle of FAT and it's derivatives such as exFAT and FAT32 - it's a crime that such an antiquated FS is still the only universal FS between platforms and devices, and why such a godawful FS is used on embedded devices like Camera flash cards.

For storage and having the "single giant pool of data", I'm probably still going to stick with my creaky old XP Pro box and use junctions in root to point to different HDs. Kludgy, but works.

Any pretense of replacing it with WHS next year is now off, since WHS will not have the capacity to perform as a home server. Why even call it "home server"? Why not call it "Windows Home Media Storage", because that's all Vail is.

For anyone interested in utilizing a very similar product that is present in all NT and higher versions of Windows, you should read up on Dynamic Disks and Volumes. It allows you to easily pool all your drives into one drive, or even stripe them, and you can add and subtract storage dynamically. Mirroring and RAID-5 capabilities, however, are reserved for Server versions of Windows, (I haven't researched whether or not Home Server has this). This saved my butt when a RAID card died in one of our servers when we were reformatting it to repurpose, so no hardware purchase was required, it was fine in our case to take the software vs. hardware RAID performance hit.

Oh, also, Hat Monster, FAT fses are actually good performers on flash based file systems, based on some benchmarks. A quick google search will show you many that have FAT winning ahead of journaling file systems on flash, and some have argued that with a smart controller, a FAT file system would preserve the life of flash based storage better than other file systems. I would like to see more on Btrfs and ZFS than what I can find so far, most of what I find compares them to ext4 and not so much anything else. I do agree that ZFS and Btrfs are excellent file systems, and I plan to use ZFS on my next home "storage server." It's just there are still use cases for FAT where performance is concerned, you want a camera to write to a card really really fast...

I just did a quick Google search for a linux-based system that has most of the features that Drive Extender has, and I found this blog post: http://www.pommepause.com/blog/2009/12/ ... ing-samba/

I haven't tested it, but it seems like it does the exact same thing that Drive Extender does. That means one can build a linux-based file server without raid (and without windows licensing), and still get the "main" feature of WHS.

On another notion - thanks Ars! I've been looking around for a new storage-solution for my home data, and I considered WHS up until this article. Time to go linux, it seems.

Yeah... I wouldn't recommend using a Linux solution for this unless the Linux solution is really already widely used AND/OR you have lots of Linux experience.

The reason Drive Extender is taken off, more or less, is because it's kinda of a broken design. The concept is lovely, but in practice it's going to be difficult to get right. Any other non-Microsoft solution is going to have similar problems, I'm afraid.

Both of these are more then just file servers, although you can use them for that. Setting up network users, internet gateways and firewalls, email solutions, VPN, etc etc etc.

In terms of integration into Windows they provide a lot of features, but are still a bit like NT was when it comes to setting up a network domain controller. Meaning that they can't do what Microsoft SBS can do when it comes to things like Active Directory.

Probably what most people in this thread would be interested in would be FreeNAS since the ZFS pooled storage would allow you to extend the storage. It features things like checksum'ng data so you never have to worry about files 'bitrotting'. The file system will detect and do it's best to automatically repair any sort of damaged file or whatever that may be caused by faulty storage or disk corruption. That sort of thing.

In the not-to-distant future with technology like BTRFS, OpenChange, and Samba 4 people are going to be able to provide solutions based on Linux or other Unix-like systems were you can effectively have a drop-in replacement for Microsoft SBS with full AD compatibility with both clients and servers. But that's going to be a while from now.

What's the difference between drive extender and Windows XP's dynamic disks? The latter allows me to pool several disks into a single logical drive, which sounds a lot like what is being described here...

Sounds kind of like they're describing ZFS features. Why can't we all adopt it and be happy?

Dynamic disks have been around for ages.

It's following the traditional model were you have File Systems resting on top of Volume Management. It's the same approach that Linux has with LVM.

ZFS is unique that it integrates all the features of software raid, logical volume management, and file systems into one solution. On top of that it adds features like compression, dedup, checksumming and it's snapshotting and volume/subvolumes are going to be better and 'more natural' then any separate RAID + Logical Volume + File system combined solution.

It's pretty nice and is certainly the next generation. Obsoletes what is available by default on other Operating Systems.

Btrfs on Linux does pretty much the same thing, but it's new. I am using it on some of my hardware, but it's going to require another year or two of testing before it's going to be trustworthy. The only distribution using it by default right now that I know of is Meego.

The lack of Drive Extender is a bit of a bugger for me, but as long as we can add drives and have them available through WHS as shares I'm not going to be too upset. The share duplication/redundancy feature is nice but I have that (hopefully) covered with backups.

Apart from the file storage system of WHS, I REALLY like the cluster-level delta backup system. I generally find when Linux peeps mention that they can replicate WHS using Ubuntu or whatever, THIS part of WHS is never mentioned. Is it possible?

I'll explain what it is so maybe someone can help:

You have x computers. They all have file abc.123 so WHS only backs up one of them, and simply references which machine has it. Therefore you can back up a bunch of machines but the storage needed to back them up is less than the individual amount of data on each machine.

What's the difference between drive extender and Windows XP's dynamic disks? The latter allows me to pool several disks into a single logical drive, which sounds a lot like what is being described here...

Drive extender gives you redundancy, at file level, and across drives of different sizes. In order to do that with dynamic disks, you *have* to get drives in matching pairs.

Well, that's crappy news. Like Barmaglot above, I was planning to rebuild my WHS box once Vail was available. Drive Extender is the #1 reason I use WHS: I have 5 drives in my server, ranging in size from 500GB to 2TB. I like that I can just plug a new drive in and not dick around with a bunch of stuff to get it working.

So, what are the best options going forward?- Continue to use WHS v1- Some Linux solution?- Dynamic disks and volumes, as mentioned by austinian above?

Maybe this is just Microsoft testing the waters, seeing what kind of uproar would be generated by saying they are cancelling the feature? [I hope]

Same here I use WHS v1 and DE is the main reason I went with it. When I was planning on building a home server I was originally thinking BSD w/ ZFS or some Linux variant but after trying out WHS it was so easy to use and configure that it just made more sense to use it. I was eagerly waiting for Vail so that DE would have the ability to fully use 2+ TB HDs, now I have 0 interest in Vail and I might have to go back to Linux or BSD when I want to move my drives to 2+ TB drives. This has to be one of the worst MS decisions ever and and honestly there is not any other feature in WHS except DE that I can think of that I really use and find absolutely essential.

A JBOD mode would get you _most_ of the relevant features, and is easy enough to implement that an intern should be able to do it in an afternoon. Should be an ok stop gap while implementing the real feature.

The other day I read a similar article in Anandtech, with similar complaints in the posts. It seems to me that MS has tried very hard to get this working for years, but has failed to do so. It's very likely that they've found reasons why they can't, and have simply given up. I don't see them removing this feature just "because".

What's the difference between drive extender and Windows XP's dynamic disks? The latter allows me to pool several disks into a single logical drive, which sounds a lot like what is being described here...

Drive extender just logically pools NTFS file systems into one big storage. It apparently relies on the operating system to copy around files using software on top of the file system. This has the advantage that you can just plug in any storage item of any size or type and it will 'just work'. Plus you can remove drives and plug them into other systems and that will 'just work'.

Dynamic Disks is a logical volume management solution. It runs _underneath_ the file system. So you combine drives into a storage pool then carve it up into separate logical volumes which then are formatted NTFS and can be used as 'drives' in Windows.

The only similarity is that they can pool storage and use NTFS. Other then that they are dramatically different.

Sounds kind of like they're describing ZFS features. Why can't we all adopt it and be happy?

ZFS can't expand its vdevs. If I build my server using 4x2TB drives in a RAID-Z configuration, then run out of space and want to add another 2TB, I can't. I need to either migrate all the data out, destroy the vdev, create a new one from 5 disks, and migrate all the data back, or buy N+1 (or N+2 for RAID-Z2) disks every time I want to expand; plus I need to keep the drive sizes matching, or lose capacity. WHSv1 doesn't have these limitations.

What's the difference between drive extender and Windows XP's dynamic disks? The latter allows me to pool several disks into a single logical drive, which sounds a lot like what is being described here...

I haven't played with dynamic disks in a while, but as I recall, once you've pooled them, the only way to remove a drive from the pool is to nuke the whole thing, which means finding somewhere to move all its data while that's done. With Drive Extender, you right-click the drive you want to remove, choose "Remove Drive" and wait as WHS migrates all of the drive's data to the other drives in the pool, then you remove it.

Seems a crazy move, I don't run WHS but am at a point where I really need a large amount of centralised storage in my home. I definitely don't want RAID, something like ZFS or Drive Extender would be perfect. There's not many options out there either. And now MS have removed the USP from WHS.

The lack of Drive Extender is a bit of a bugger for me, but as long as we can add drives and have them available through WHS as shares I'm not going to be too upset. The share duplication/redundancy feature is nice but I have that (hopefully) covered with backups.

Apart from the file storage system of WHS, I REALLY like the cluster-level delta backup system. I generally find when Linux peeps mention that they can replicate WHS using Ubuntu or whatever, THIS part of WHS is never mentioned. Is it possible?

I'll explain what it is so maybe someone can help:

You have x computers. They all have file abc.123 so WHS only backs up one of them, and simply references which machine has it. Therefore you can back up a bunch of machines but the storage needed to back them up is less than the individual amount of data on each machine.

It's very nifty.

With ZFS you can use it's built in Deduplication features. What happens is that you have all your machines back themselves up to a file share on your network. Then ZFS will go through and check for duplicate files and information on the file system. if the dedup feature is used it will go through and combine duplicate blocks of storage. So if you have 30 copies of abc.123 on ZFS it will only use as much space as necessary to hold one copy and just have each file name point to the same information. If somebody ends up changing the file then it will make a new copy of the changes (Copy On Write). Even if the files have different names. Plus it will combine duplicate information even if the files are named differently or have different headers and such.

Drive Extender was my main reason for wanting WHS. I really hope they DO end up implementing it as I really, really want to get a WHS, it would solve many of the issues with file storage I have and save me a lot of time/fussing around.I'm probably 6-12 months away from getting one anyway, but this will probably delay it further as I'll have to get a Drobo first. Heck, if the Drobo does a decent job, I might just look into re-purposing an old laptop w/ a linux install and bypass WHS altogether, but I'd rather not. My experience with Windows Server products has been overwhelmingly positive and I'd like to keep using what I know rather than dicking around with linux.Do the right thang MS!

I changed my file server to Vista when my last Gentoo file server died. Backups are handled with a simple daily sync.

I got tired of having to hack Windows 7 in order to add a Linux Samba share to a Library and missed indexing (Vista with Index Search 4.0 works fine). Just thought anyone considering Linux should be aware of the limitations if you want to interoperate with Windows 7.

This kind of stuff really shouldn't be as hard as it is. Major fail for Microsoft in not making Drive Extender work.

I may just stick with the last version of software for my HP Mediasmart server and then look at hacking it to Windows 7 or some such later.

The other bugaboo about WHS is that being based upon Windows Server 2003 means many third party apps require a WHS specific version or a lot of tweaking to make work. It might be easier to just run Windows desktop and let it be a media server for both the Xbox via Media Sharing and iTunes via Home Sharing without hassles.

Microsoft is really starting to piss me off. They're developing a very arrogant attitude, and more and more often their response to requests for features or fixes are resolved with "not a feature" or "no fix".

Sounds kind of like they're describing ZFS features. Why can't we all adopt it and be happy?

ZFS can't expand its vdevs. If I build my server using 4x2TB drives in a RAID-Z configuration, then run out of space and want to add another 2TB, I can't. I need to either migrate all the data out, destroy the vdev, create a new one from 5 disks, and migrate all the data back, or buy N+1 (or N+2 for RAID-Z2) disks every time I want to expand; plus I need to keep the drive sizes matching, or lose capacity. WHSv1 doesn't have these limitations.

It's not recommended, and you have to force the add command, but you can add vdevs of any size/configuration to an existing pool.

Have a pool with a 4-disk raidz1, and want to add a 2-drive mirror? No problem (I run this at home).

Have a pool with a 4-disk raidz1 and a 2-drive mirror, and want to add a 6-disk raidz2? No problem.

Only have 4 drive slots in your system, and running with a 4-drive raidz1? Then just replace each disk with a a larger one, wait for it to resilver, then export/import the pool. Voila! All that extra space is now available.

The only 2 real downsides to ZFS is that you can't change the configuration of a raidz vdev (go from a 4-drives raidz1 to a 5-drive raidz1; or from a 4-drive raidz1 to a 4-drive raidz2, for example), and you can't shrink the size of a pool (remove vdevs, replace drives with smaller ones, etc).

Help me out here... I'm having trouble understanding who uses this product and why. With storage dirt cheap, why not just throw a couple of 2 TB drives in your case and set up libraries in Win 7 that pull whatever folders you need together in one place.

Why does anyone care if their various drives are treated like one "pool" of storage? At least, anyone competent enough to set up a home server?

Help me out here... I'm having trouble understanding who uses this product and why. With storage dirt cheap, why not just throw a couple of 2 TB drives in your case and set up libraries in Win 7 that pull whatever folders you need together in one place.

Why does anyone care if their various drives are treated like one "pool" of storage? At least, anyone competent enough to set up a home server?

Seriously, what's the point?

Help me out here... I'm having trouble understanding who thinks £150 is that easy to come by.

I have 6 drives connected to my Desktop PC ranging from 60GB to 1.5TB. Whilst I do not use WHS or DE I can understand why this feature is a deal breaker for many people.

Help me out here... I'm having trouble understanding who thinks £150 is that easy to come by.

I have 6 drives connected to my Desktop PC ranging from 60GB to 1.5TB. Whilst I do not use WHS or DE I can understand why this feature is a deal breaker for many people.

But I seriously don't understand - WHS doesn't get you any more storage, it just changes how you interface with it. You'd still have the same 6 drives connected. You don't somehow save money on hard drives by using WHS.

I'm not being snarky, I honestly don't understand what the point of Drive Extender is.